It may or may not fit the bill but I have found my Leatherman Wave to work well as my EDC knife.

The thumb opening slot allows quick one-handed opening and the blade locks open. This operation is as quick and as sure as it gets for right handed people. Lefties may need a bit more training and dexterity but not to much.

I keep it in the sheath on my belt oriented so that the straight blade falls under my thumb for immediate use but if I want a serrated blade instead of the straight I simply roll the knife over, still using one hand only, and the same thumb opening and locking features are available on the serrated blade.

The size is slightly thicker and heavier than most single blade folders with similar sized blades but not by so much as to be a burden. The fact that you get saw, file, pliers, several screwdriver blades and a scissors in a package just a little bulkier than a single blade folder is a pretty big bonus in my book. The size of these tools is a bit larger, more functional, than many multi-tools. The steel in the blades is fair to good. Functional but not exceptional.

Cost runs about $70 but as low as $55 on sale.